The main opposition Liberal Democratic Party is leading polls a month before Japan’s parliamentary election. But many voters are undecided.

The Yomiuri newspaper, Japan’s largest, found the LDP had support from 26 per cent of voters while 13 per cent said they backed the ruling Democratic Party of Japan. Support for two new parties that plan to merge rivaled the DPJ in the survey.

The poll showed that 43 per cent of respondents backed no particular party.

Prime Minister Yoshihiko Noda dissolved parliament on Friday and called elections for December 16. The poll was conducted Friday and Saturday.

LDP led Japan for most of the post-World War II era. The Yomiuri poll and earlier surveys show it is likely to win the most seats but would have to form a coalition to govern.